Which sentence contains an error in the use of apostrophes?

A.
When he writes, my little brother makes b's for d's.

B.
Do not use &s or text-messaging abbreviations in your writing.

C.
Oh, dear, he's written all these 4s backwards.

D.
As in this font are not very legible.
I'm not sure about this one.

Question

Which sentence contains an error in the use of apostrophes?
  
 
 A.
When he writes, my little brother makes b's for d's.
 
 B.
Do not use &s or text-messaging abbreviations in your writing.
 
 C.
Oh, dear, he's written all these 4s backwards.
 
 D.
As in this font are not very legible.
I'm not sure about this one.

anonymous · Answer

D

keeli_grace · Answer

So that would make it A's, correct?